1. Field of Invention
This invention relates to the field of using laser energy for fracturing a mass such as a rock.
2. Description of the Related Art
Fracturing or breaking solid materials is a method used by mining as well as other industries. Fracturing is done by drilling, blasting, scraping, ripping, chipping and cutting. Water-jet drills are used for exploration and blasting in loose or weakly bonded materials. Hydraulic mining uses jets or streams of water for excavation of loose materials. U.S. Pat. No. 5,004,166 describes an apparatus that uses a pulsing laser to fracture masses, such as rocks. The apparatus of U.S. Pat. No. 5,004,166, also uses a monitoring laser beam for measuring the resonant frequency of rocks. The pulsing laser beam is adjusted to match that resonant frequency. Pulsing the laser beam at the resonant frequency of a rock imparts more destructive energy than is imparted by pulsing at other frequencies. The inventor of the present invention invented U.S. Pat. No. 5,004,166. U.S. Pat. No. 5,004,166 is incorporated herein by reference.
Conventional streams of water have not proven useful for excavating hard rock unless pressurized water can invade pre-existing cracks. Conventional laser beams (short pulses or continuous beams) have provided neither economical nor practical means of excavating hard rock.